The goal of this Team is the clinical application of the methods of Optical Pharmacokinetics (OP) and Elastic Scattering Spectroscopy (ESS) for the management of photodynamic therapy (PDT) in the treatment of cancer and other pathologies. OP will be used to monitor local tissue concentrations andbiodistribution of PDT agents, providing patient-specific information on dosage and optimal time foractivation. ESS will be used as an adjunct to follow the response of tissues to treatment by sensingchanges in the tissue optical properties. The short-term objectives are to detect and resolve any limitations for clinical implementation, to demonstrate that these are clinically "friendly" modalities, and to generate the computational/numerical tools that will provide the measured results in real time during clinical treatment. The ideal implementation of PDT requires delivery of both the proper drug dosage and the proper light "dosage", which in turn requires understanding of the optical properties of the tissue and knowledge of drug concentration in the tissue of interest. In vivo measurements would provide information on patient-patient variability in the uptake of the drug and, therefore, make possible individual dosimetry for PDT. In addition, the site-specific time history of the drug is especially important because the photoactivation should be done when the ratio of drug concentration in the tumor to surrounding tissue is at a maximum. The Primary Projects address both animal and clinical studies to answer a series of questions aimed at validating the capabilities and sensitivities of the spectroscopic methods and assessing the implications of those aspects of the methods that impact clinical utility and health-care significance. The Technical Support Core-provides-the-instrumentation-and the mathematical tools to all Projects and facilitates the data analysis. The Administrative Core provides the superstructure of the Team, especially to facilitate communication and information sharing, both within this Team and among all the Teams of the Network.